This invention relates generally to ultrasound systems that image anatomical structures, and more particularly, to a method and apparatus for displaying computer-coordinated markers simultaneously on dual ultrasound images of different modes in “real time.”
Ultrasound contrast imaging is used for tumor detection and characterization in some parts of the world. Microbubbles are used today as contrast agents. A physician will generally inject the contrast agent into the patient. The contrast agent is used to isolate and identify where in an organ, for example, in a liver, to perform a biopsy. Generally, there will be a biopsy bracket on the ultrasound probe. A display will provide a centerline and two guidelines giving a range within which a biopsy needle will be guided. In addition, a depth marker may also appear on the screen and the lesion may be measured.
The contrast agents are able to enter blood microcirculation for several minutes without breaking under a low mechanic index acoustic field. Contrast agents increase blood backscattering signal strength and make blood flow from small vessels visible in images in which they would be masked by a surrounding tissue echo. Because of differences in vascularity, enhancement patterns are different between normal tissue and tumors, as well as between different tumor types. The differences in enhancement patterns are used for tumor detection and characterization.
To obtain improved contrast performance, contrast imaging suppresses the tissue background to increase the contrast to tissue ratio. When a tissue background is perfectly suppressed, a target becomes difficult to see before contrast injection. A dark tissue background causes difficulty in maintaining the small lesion in an image plane due to movement from patient breath, patient motion and probe motion. For diagnosis, it is important to know the exact location of the lesion in the image and to see the contrast enhancement dynamic pattern over a period of time. Thus, a B mode image is often used as reference for monitoring the lesion position and a contrast image is displayed alongside the B mode image in real time in a dual imaging mode. The dual image mode makes it simpler to monitor the target image, but it is sometimes still difficult to know the exact position of the lesion in the contrast mode image when the lesion is small. Moreover, contrast agents do not remain in the body for an extended time. Hence, contrast examinations have a limited viewing time. In the meantime, the user (e.g., the physician) is busy storing images and clips to a hard drive in the ultrasound machine and has to concentrate on what he or she is doing during the relatively limited examination time.
Ultrasound systems may use recording systems to store a series of images. Video recorders or a digital memory are incorporated into many conventional ultrasound systems. The information stored by and played back from a digital memory is generally limited by the analysis being performed during recording. The reason for this limitation is that a conventional digital memory receives data produced after the echo signals have been processed and prepared for display. Therefore, the digital memory stores only the data resulting from a particular processing operation carried out upon the echo signals at the time the patient was examined. The processing operation is determined by the present mode of operation and parameter settings. Thus, processed data that is stored may ignore and/or eliminate certain information from the echo signals. This ignored or eliminated information cannot be recovered. For example, an abnormality recognized in a recorded image after the patient has left cannot be analyzed in greater detail unless the patient returns for a new scanning session and then only if the abnormality present during the original scanning session is again detected. Accordingly, images that are recorded while inaccurate or less than optimal parameters are set may be useless. Thus, increases in the length or number of ultrasound scanning sessions may result, thereby increasing patient exposure time, patient discomfort and procedure costs. Furthermore, studies employing contrast agents are limited in the number of different analyses that can be performed during the rapid decay of the contrast agent.